Check engine light?

EGR mostly closed except for certain load conditions when the combustion gases need to be cooled for emissions. A totally closed EGR should not present any problems in drivability. It's when it sticks open that the engine will not idle properly, or even stall, as then it's a vacuum leak.

I suspect your problem is not EGR.

 

Here's what I'd do... Pull the vacuum line attached to the EGR valve and plug it. The EGR is opening when it shouldn't, causing the bucking. Disable it.

 

Thanks for the responses so far.

I should have noted that the "check engine" light is indeed on, solid rather than flashing.

I appreciate the tips about what I might do to the car myself, but am not in a position to do them: I am visiting friends and neither have the tools or the ability to get under the car. Plus it's a Sunday, when a lot of places are closed.

So for me the only issue is whether driving 400 more miles at a lower speed that doesn't cause that bucking -- a perfect term for what I experienced -- would risk damaging the catalytic converter (and/or something else), or if damage is only likely if I drive at high speeds that trigger the problem. Thanks!

 

I did some Googling for my problem, now that I understand it better, and found this:
"As to possible damage; yes, the missfiring will eventually cause damage to your catalytic converter. When and engine missfires, the fuel in the cylinders must still exit the cylinder. It exits out through the exhaust valve and goes through the exhaust system. The catalytic converter is part of the exhaust system. Unburned fuel is pure hydrocarbons; what the catalytic converter is meant to convert to harmless byproducts. The catalytic converter is meant to do this with tiny amounts of unburned hydrocarbons; not cylinders full of pure unburned hydrocarbons in the form of raw gasoline. This missfiring will take it's toll on the converter and eventually ruin it."

That makes perfect sense to me (as a non-expert). Assuming it's correct, the only real question I have becomes, can such damage occur during a 400-mile drive if I do not cause the misfiring, or will even driving at lower speeds cause damage. I have to decide whether to hit the road in the next hour or so -- here's to hoping someone sees this in time!

Thanks.

 

Get the codes pulled at an AutoZone, this will give you an idea of what is going on.

At least remove the top vacuum hose on the EGR and plug it with a pencil or something. This takes no tools.

Just because the cars isn't shaking doesn't mean the engine isnt operating in a overly rich or too lean condition.

 

my 95 I4 wagon had a similar symptom, an intermittent EGR light would come on while driving and then go off again. On a long distance trip we were cresting a pass on I5 in cruise control with the engine working pretty hard. All of a sudden the car starts clattering and making a TERRIBLE racket, I immediately tapped the brake dropping the car out of cruise and applied the throttle, our speed dropped about 5mph and the noise stopped.

Never any issues after that (no more passes) but when I pulled the EGR the tube was 100% plugged. I swapped it out with a fresher Solara unit and a newer modulator that I'd cleaned out. No more EGR light and the (scary) noise hasn't reoccurred.

I cannot figure how a bad EGR would cause this, but it did.

 

Like carsrus said, the vacuum line to the EGR is super easy to get to, and requires zero tools. It's the part with a blue label on it in the pic below. There's one vacuum line to it, on top. Pull and plug that line.

 

Thank you all for your comments, for which I am grateful. Now that I have completed a Mich.-to-Mass. move and have some spare time again I owe you a follow-up about what happened, and what I eventually learned about this problem.

That morning I decided, based on my experience with driving the car successfully at a lower speed, to leave St. Louis for Oklahoma, looking from the highway for an exit with an Autozone or O'Reilly's or some other auto parts store where I might be able to buy an EGR valve and borrow some tools and try to do the work myself, which I had watched being done on YouTube videos; or, at least, I'd plug it up, as suggested. (It was a Sunday, an no mechanics seemed to be working, other than those who just do oil changes and tires.) Just a few miles of driving along I-44 brought about more of the bucking but at a lower speed, and then the car unexpectedly lost all power (with the battery light and engine oil light coming on) and I had to coast to the shoulder and wait to be towed. (Not an enjoyable experience waiting for a tow on one of those St. Louis days when it's 90 and muggy.)

Being from out of town, and knowing that a Toyota dealership was more likely to have needed parts on hand than an independent mechanic, I had the car towed to one of the city's dealerships. The mechanics there took a look on Monday, and here's what they found: the EGR valve was indeed broken, but was not the cause of the bucking (or, of course, the power loss). The cause, of all things, was that when my independent mechanic back in Michigan had done a timing belt/water pump replacement he -- actually, the young apprentice whose job it was to do the final steps of "closing up" the patient -- had mistakenly routed a wire (Camshaft Position Sensor Circuit, if I read the report correctly) in the wrong place, putting it so close to the exhaust manifold that after about 400 miles of high-speed driving on a 90-degree day the insulation melted and the wires fused. THAT was what caused the bucking. The St. Louis mechanics were able to fix that easily enough ($70 for parts and labor, which involved soldering), but their diagnostic check also showed code numbers indicating that my alternator was going bad, so I had that replaced. (The five code readings I got were P0340, for the camshaft circuit, P0401 for the EGR valve, P0440 for an unrelated emissions issue I've long known about, and P1300 + P 1310, for igniter circuits 1 & 3.) Since the car had around 176,000 miles and I had no recollection of having replaced the alternator before this seemed plausible, so I authorized that work.

I was able to pick up the car later in the week and headed back north from St. Louis, having made my trip to Tulsa in a rental. (No loaners at the dealership.) A day or two later the car began to develop trouble starting, so that by the fifth or sixth day it would barely start at all. I had arranged to have my original independent mechanic replace the EGR valve -- in St. Louis the dealer wanted $400, which I knew to be crazy, while I figured that my original mechanic owed me big for the mistake with those wires and would give me a discount, which he did -- so I decided I'd let him check to see if in St. Louis they'd given me a bad alternator, which I figured might be at the heart of this problem. It instead simply turned out that the battery had gone bad. The odd thing is that in St. Louis they checked the battery (of course), and told me it was fine. So the possibilities are either that the battery went bad out of sheer coincidence -- after all, on 90-degree days older batteries do have a greater chance of dying -- or that in St. Louis they hadn't recharged the battery to the proper level and stress from that did it in, or earlier stress from the problems the car encountered caused trouble for the battery. (When I brought the car to the Michigan mechanic he noticed that the battery was slightly bowing outward, a sign of going bad -- something presumably they would have noticed in St. Louis if it was already visible.)

I, of course, have no way of knowing what caused the battery to go, but since its replacement the car runs perfectly again. And the new EGR valve is one less thing to worry about. And, since I've now moved to Massachusetts, a state with rigorous emissions restrictions for registering a new car, I'll finally have to take care of that other emissions issue. So the car continues to be an ongoing project, but at least it drives without further problems.